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Production of multimodal polythylene

a polyethylene and multi-modal technology, applied in the field of polyethylene preparation, can solve the problems of high molecular weight polyolefins that are difficult to process and can be costly to produ

Inactive Publication Date: 2002-02-12
FINA RES SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, high molecular weight polyolefins can be difficult to process and can be costly to produce.

Method used

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  • Production of multimodal polythylene
  • Production of multimodal polythylene
  • Production of multimodal polythylene

Examples

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example 2

This Example used the metallocene ethylene bis (4,5,6,7-tetrahydro-1-indenyl) zirconium dichloride of Example 1 in two reactors in series to produce a bimodal LLDPE polyethylene resin. The catalyst comprised 4 wt % on the support.

The catalyst was employed in a copolymerisation process to produce a polyethylene copolymer. In a first reactor of two serially connected reactors, the ethylene comprised 4 wt % and the hexene comprised 3.6 wt %, each in the off gas. The polymerisation temperature was 70.degree. C. and the residence time was 70 minutes. Hydrogen was added to the reactor in an amount of 0.2 Nl / h.

This first polyethylene product was used to constitute a first LLDPE fraction of an LLDPE bimodal resin which comprised a chemical blend of two separate polyethylenes. The second polyethylene produced in the second of the serially connected reactors using the same catalyst as for the first reactor comprised an LLDPE polyethylene.

In the polymerisation process to produce the second pol...

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Abstract

A process for the preparation of polyethylene resins having a multimodal molecular weight distribution which comprises:(i) contacting ethylene monomer and a comonomer comprising an alpha-olefin having from 3 to 10 carbon atoms with a first catalyst system in a first reactor under first polymerisation conditions to produce a first polyethylene having a first molecular weight, an HLMI of not more than 0.5 g / 10 min and a first density of not more than 0.925 g / ml and the first catalyst system comprising (a) a metallocene catalyst comprising a bis tetrahydroindenyl compound of the general formula (IndH4)2R''MQ2 in which each Ind is the same or different and is indenyl or substituted indenyl, R'' is a bridge which comprises a C1-C20 alkylene radical, a dialkyl germanium or silicon or siloxane, or an alkyl phosphine or amine radical, which bridge is substituted or unsubstituted, M is a Group IVB transition metal or vanadium and each Q is hydrocarbyl having 1 to 20 carbon atoms or halogen; and (b) a cocatalyst which activates the catalyst component;(ii) providing a second polyethylene having a second lower molecular weight and second higher density than the first polyethylene, the second polyethylene having been produced using a catalyst other than the bis tetrahydroindenyl compound; and(iii) mixing together the first and second polyethylenes to form a polyethylene resin having a multimodal molecular weight distribution.

Description

BACKGROUND TO THE INVENTIONThe present invention relates to a process for the preparation of polyethylenes, having a multimodal molecular weight distribution, more particularly a bimodal or trimodal molecular weight distribution and exhibiting outstanding mechanical properties for blow-molding, film and pipe applications.DESCRIPTION OF THE PRIOR ARTPolyolefins such as polyethylenes which have high molecular weight generally have improved mechanical properties over their lower molecular weight counterparts. However, high molecular weight polyolefins can be difficult to process and can be costly to produce. Polyolefins having a bimodal molecular weight distribution are desirable because they can combine the advantageous mechanical properties of high molecular weight fraction with the improved processing properties of the low molecular weight fraction.For many HDPE applications, polyethylene with enhanced toughness, strength and environmental stress cracking resistance (ESCR) is import...

Claims

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Application Information

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IPC IPC(8): C08F110/02C08F210/00C08L23/00C08F110/00C08L23/06C08L23/08C08F210/16C08F4/00C08F4/659C08F4/64C08F4/642C08F10/02C08F4/6592C08L23/04
CPCC08F110/02C08F210/16C08L23/06C08L23/0815C08F4/65925C08F4/65927C08F2/001C08F4/24C08F4/65916C08L2314/06C08L2205/025C08L2308/00C08L2314/02C08L2314/04C08L2205/02C08L2666/04C08F210/14C08F2500/01C08F2500/02C08F2500/13C08F2500/07C08F2500/12C08F2500/05C08F2500/08
Inventor DEBRAS, GUYRAZAVI, ABBASMICHEL, JACQUES
Owner FINA RES SA
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